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Abstract

This study examined the opportunity of implementing modern yarder machinery to increase
the productivity and worker safety of cable logging operations within New Zealand. Cable
yarding equipment used in New Zealand is generally based on designs from pre-1980 with
the majority of the machines built around that time in the Pacific Northwest, USA. New
yarder designs have a number of features that may give them an advantage, including being;
smaller, quieter, more fuel efficient, safer and more ergonomic to operate. These benefits can
be of even greater value as the forest industry transitions from predominantly larger scale
commercial plantations, to a significant proportion of woodlot scale operations.
Field studies ranging from three to five day of duration were carried out on three new
machines believed to have potential in New Zealand; the Active 70 at two locations in the
central North Island region of New Zealand, the Koller 602h in the Gisborne region of New
Zealand and for comparison the Koller 507 in Austria. The studies focussed on assessing
productivity and ergonomic advantages. Productivity was measured with a time and motion
study and the potential ergonomic advantages were assessed using choker-setter heart rates
and machine noise emissions.
The time and motion study found a productivity level for the Active 70 of 23.5m3/SMH with
a utilisation rate of 65% at site one and 24.5m3/SMH at a utilisation rate of 76% for site two.
The productivity for the Koller 602h was 21.0m3/SMH at an utilisation rate of 55% and
7.9m3/SMH for the Koller 507 at an utilisation rate of 55%. Productivity was deemed to be
negatively impacted by poor site conditions for the Active 70 and Koller 507, and utilisation
was low for the Koller 602h which was mainly attributed to the lack of crew experience with
the new machine. Choker-setter heart rate results showed choker-setters to be working at the
level of ‘hard continuous work’ (‘relative heart rate at work’ over 30%, but less than 40%). In
this study the motorised carriage used at the first Active 70 study site offered no ergonomic
advantages over the traditional North Bend system at the second site. Decibel analysis found
that the modern equipment was significantly quieter, resulting in smaller zones in which
hearing protection is required. In particular, the Koller K602hrecorded 70dB at 5 meters
during operation, well below the 85dB level that is common recognised as the decibel
threshold for hearing damage.
During these case studies the machines all operated below the average New Zealand
productivity rate of 26.3m3/SMH and no clear ergonomic advantage was established for the
choker-setters. As such these machines are not likely to out-compete existing machinery
choices in either productivity or choker-setter work rate. However, cost-benefit analyses were
not possible because of limited information about operating cost and the absence of truly
comparable settings. Advantages such as the advanced control systems and lower noise
levels, while still achieving respectable productivity figures, indicate that they are viable
alternatives for New Zealand cable yarding if applied correctly.